Intervening with CBTi prior to a PTSD-specific treatment and measuring biomarkers longitudinally, will allow for the testing of specific effects of sleep improvement on PTSD, depressive symptoms, objective aspects sleep and stress and inflammatory markers, thereby advancing basic understanding of biobehavioral mechanisms in PTSD and depression. Importantly, the proposed approach utilizes a treatment sequence that may appeal to trauma survivors with post-traumatic event symptoms who may be resistant to or unprepared to fully engage in standard PTSD treatments. Confirmation of the study hypotheses could support immediate translation of the findings to clinical practice.